A Conservative metro mayor has called on the Government to offer “full backing” for a multi-billion pound North Yorkshire mine project he says is essential to the local economy.

Tees Valley mayor Ben Houchen is urging the Treasury to guarantee $2bn of the $3bn financing Sirius Minerals needs to extract the fertiliser polyhalite at Woodsmith Mine near Whitby and market it internationally.

A Treasury guarantee would mean that lenders will be repaid in full and on time, irrespective of the project’s performance, transferring the risk to the Government in return for a fee.

The Government scheme was set up following the 2008 financial crisis to make sure important infrastructure projects could access the capital they need.

Once extracted in the country’s first new fertiliser mine in a generation, polyhalite, a high grade form of potash and multi-nutrient fertiliser which increases yields, would be taken to Sirius’s Tees Valley facility for global export.

Sirius completed its purchase of a 284-acre site at Bran Sands, east of Middlesbrough. Mr Houchen says the whole operation will create more than 2,500 jobs and £2.5bn of annual exports at full production.

Before meeting Treasury Minister Robert Jenrick yesterday, Mr Houchen wrote to Chancellor Philip Hammond re-emphasising his support for the “transformative economic impact” the mine project would have on the local economy.

He wrote: “Sirius Minerals’ project is the single largest private investment in the North right now and undoubtedly one of national importance. Thousands of jobs will be created and the Tees Valley stands to benefit enormously.

“Sirius Minerals’ decision to purchase Bran Sands and more recently its material handling facility site at Wilton represents a huge vote of confidence in our area and our workforce.

“It is a move that will deliver real, visible results very soon and provide a solid basis for further expansion in the future.

“However for the project to proceed, this game-changing development needs the ongoing and full backing from Government.”